Inflatable restraint systems, commonly referred to as airbag systems, which deploy automatically in the event of a collision to shield and cushion the occupants of a vehicle from the hard surfaces within the passenger compartment, have become very popular in modern motor vehicles. Many types of inflator devices for inflating the airbag cushion in such systems have been disclosed. Such inflators should be capable of releasing a sufficient quantity of a non-toxic gas to inflate the airbag cushion in a very short period of time. Additionally, the inflator needs to provide a high degree of reliability over the extended temperature range in which modern vehicles are expected to operate, and over the extended lifetime of the vehicle.
One of the disclosed inflator designs relies on a stored compressed gas which is released to inflate the airbag. Another design relies on the ignition of a solid gas generating material to produce a sufficient quantity of gas to inflate the airbag. A third type of inflator relies on the combination of an inert stored compressed gas and the combustion of a solid gas generating material. While these designs are functional to provide the gas needed to inflate an airbag, they each have disadvantages. The designs which rely solely on compressed gas must provide a relatively strong gas storage container, the relatively thick walls of which increase the weight and bulk of the airbag assembly, a concern to those vehicle manufacturers who seek to minimize the weight of such vehicles. The designs which rely on the ignition of a solid gas generant material usually result in a generated gas which contains solid particulate material at a sufficiently elevated temperature that it requires further conditioning, such as filtering and cooling, before it encounters the fabric cushion of the airbag assembly.
Some of the more recent inflator designs rely on fluid fuels and oxidants which, in addition to lower manufacturing costs, offer advantages such as, inter alia, cleaner generated gases which contain little or no solid particulate matter, and which can be provided at relatively low temperatures and with relatively low concentrations of incomplete products of combustion. Some of these designs are more fully described in U.S. patent application Ser. No. 08/252,036, entitled FLUID FUELED AIR BAG INFLATOR, now U.S. Pat. No. 5,470,104, filed by Bradley W. Smith and Karl K. Rink and commonly assigned with this application. Application Ser. No. 08/252,036 is hereby incorporated by reference.
A need exists, however, to improve the design of the known fluid fueled inflators to provide structural characteristics which provide regulation of the gas storage, heating and release procedures whereby the proper design of the structure enables the inflation characteristics of the airbag to be tailored to meet specific requirements. Such designs must also provide for the flammable components to be held safely over the expected lifetime of the vehicle. The designs further need to reliably produce an inflation gas which does not contain significant amounts of relatively toxic incompletely combusted gases. Additionally, the designs must be capable of being rapidly and safely manufactured and filled with the flammable mixtures. Finally, to ensure proper operation, the ignition process must be reliable.